Arrangement for operating a consumer in a motor vehicle

ABSTRACT

An arrangement for driving a consumer in a vehicle is suggested. The arrangement has at least two switch elements for influencing the current flow through the consumer. For each switch element, the current flowing through this switch element is monitored and evaluated for detecting a short circuit.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 4,951,188 discloses an arrangement for operating aconsumer in a vehicle. There, an output stage is a bridge circuit havingfour switching elements is suggested. The current passing through theconsumer, which is connected in the bridge diagonal branch, is detectedand compared to pregiven threshold values. If the current through theconsumer exceeds a pregiven maximum value, then a short circuit isassumed in the region of the consumer and the output stage is switchedoff in such a manner that a switch-on pulse-duty factor of 1% resultsfor carrying out an emergency operation. Short-term disturbances canoccur, for example, by disturbing radiation. Even for these short-termdisturbances, the output stage can be switched off with this procedureand an emergency operation initiated. In this way, the availability ofthe arrangement is limited.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an arrangement foroperating a consumer wherein the availability is improved especially inconnection with short-term disturbances without affecting theoperational reliability of the arrangement.

According to a second aspect of the invention, the arrangement foroperating the consumer is to be configured in such a manner that anintegration of the entire arrangement in one component is made possible.The coupling of this component to a microcomputer for driving anelectric positioning motor in combination with the adjustment of a poweradjusting element of an internal combustion engine such as a throttleflap or a diesel injection pump is made possible.

Short disturbances in the area of an arrangement for operating aconsumer are detected with the procedure according to the invention.However, these disturbances do not necessarily lead to an unwantedeffect on the operation so that the availability of the arrangement isconsiderably improved.

It is especially advantageous that the current through each switchingelement of the arrangement is detected and is checked as to whether thecurrent exceeds a pregiven maximum value.

A time component is started when the maximum current is exceeded and afault is only then detected when the maximum current is exceeded for apregiven time. In this way, short-term disturbances do not lead to aswitch-off of the arrangement. The fault detection takes placeindependently of the clocked driving signal.

In this way, errors are also detected when the drive signal continuouslyexhibits a high level or a low level.

It is further advantageous that the operational reliability of thearrangement is not affected by counting the detected short disturbancesand by a fault reaction when there is a pregiven number of detecteddisturbances.

In this context, it is further advantageous that current-limiting meansare provided which limit the current through the particular switchingelement to a pregiven maximum value so that a rapid reaction even forshort-term disturbances takes place which avoids unwanted operatingconditions and yet does not limit the availability of the arrangement;whereas, a long-term check ensures operational reliability by detectingthe disturbances and by counting the detected disturbances during alonger continuous fault case and/or by means of the time condition.

For a clocked drive, it is especially advantageous that the switchelement, which is detected as being defective during a drive pulse, isagain switched on with the next drive pulse when the fault counter hasnot yet reached the predetermined counter position.

Decrementing the fault counter for correctly operating switch elementsleads in an advantageous manner to the situation that distributed faultsdo not lead to a switch-off. These distributed faults occur at differenttime points during the operating duration of the system.

An integration into a standard IC-housing is made possible by theadvantageous assembly of the drive arrangement without undertakingrestrictions with respect to the extent of operation. This leads to avery economical and reliable component.

In addition to the above-outlined current monitoring with the providedreaction measures, it is especially advantageous to provide a supplementwith additional protective mechanisms such as an undervoltageprotection, overvoltage protection, overtemperature protection and/or amonitoring of the voltage at the charging pump of the switch elementswhich switch the supply voltage.

Furthermore, it is advantageous that a microcomputer can, under specificpreconditions, can again switch on a drive unit detected as defectivewhile decrementing the fault counter. The microcomputer can, in the caseof a fault, attempt to restart the output stage a few times.

If the counter counts, for example to 10, the fault counter is filledafter 400 microseconds for an assumed clock frequency of the computer of25 kHz. This means that, for a temporary fault case (for example EMV) inthe millisecond range, the counter is immediately filled. For thisreason, it is purposeful that the microcomputer attempts at least onceto again start the output stage in that the microcomputer decrements thefault counter. This procedure has been shown to be exceptionallyadvantageous.

Special advantages result from the procedure of the invention with theapplication for driving a direct-current motor or a step motor foractuating a power adjusting element of an internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail with respect to theembodiments shown in the drawing. Thus, FIG. 1 shows an overview blockcircuit diagram of a control system equipped with an arrangementaccording to the invention, whereas FIG. 2 shows a detailed blockcircuit diagram of the arrangement of the invention in the context of afirst embodiment. A detailed block circuit diagram of the arrangement ofthe invention is shown in FIG. 3 in the context of a second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a microcomputer 10 as well as an arrangement 12 foroperating a consumer 62. The microcomputer 10 has the input lines 14 to16 which connect the computer to measuring devices 18 to 20. A firstdrive line 22 and a second drive line 24 connect the microcomputer 10 tothe inputs E1 and E2, respectively, of the arrangement 12. In thepreferred embodiment of the drive of a motor, the signal supplied to theinput E2 or E1 is obtained by inverting the signal outputted onto thelines 22 and 24, respectively. A further connecting line 26 connects themicrocomputer 10 to the input D1 of the arrangement 12. Furthermore, aconnecting line 28 connects the output FF of the arrangement 12 to themicrocomputer 10. In addition, a second microcomputer 11 is providedwhich is connected via the line 27 to the input D2 of arrangement 12.This second computer has, in the preferred embodiment, other tasks(gasoline injection and ignition). For this purpose, input lines 1000 to1002 are connected thereto from measuring devices 1004 to 1006. Themicrocomputers 10 and 11 exchange data and control variables via a bussystem 1008.

The preferred embodiment of the arrangement 12 shown in FIG. 1 isadvantageously configured as an integrated component and includes afull-bridge output stage for driving an electro-magnetic consumer whichis arranged in the diagonal of the bridge circuit. The bridge circuitshown includes four switch elements 30, 32, 34, 36 which, in thepreferred embodiments, are configured as MOS field effect transistors.

A connecting point of switch element 30 and a connecting point of switchelement 32 are connected to the positive pole 42 of the operatingvoltage via the lines 38 and 40, respectively. The second connectingpoint of the switch element 30 is connected to the first connectingpoint of switch element 34 via a connecting line 44. The otherconnecting point of switch element 34 is, in turn, connected to thenegative pole 48 of the operating voltage via the line 46. In acomparable manner, the second connecting point of the switch element 42is coupled via the line 50 to the first connecting point of the switchelement 36 and the other connecting point of switch element 36 isconnected via the line 52 to the negative pole 48 of the operatingvoltage. A line 54 leads from the connecting line 44 via a currentdetecting resistor 55 to the connecting point 56 of the arrangement 12;whereas, a line 58 leads from the line 50 to the second connecting point60 of the arrangement 12. The consumer 62 is connected between theconnecting points 56 and 60.

In the preferred embodiment, the consumer is a direct-current motor,whereas, in other embodiments, the consumer 62 can be the winding of astep motor in a likewise advantageous manner. For the step motorapplication, an arrangement 12 is provided for each phase and eacharrangement is connected to the microcomputers in the manner shown.

A drive element is assigned to each of the switch elements (30, 32, 34,36) to actuate the drive elements. The drive elements are connected tothe control connections of the switch elements. Thus, the line 64connects the drive element 66 to the switch element 30, the line 68connects the drive element 70 to the switch element 34, the line 72connects the drive element 74 to the switch element 32 and the line 76connects the drive element 78 to the switch element 36. The assembly ofthe drive elements is described below with respect to FIG. 2.

The switch elements are so-called current-sensing MOS-FETs. These switchelements have an output via which a signal is outputted which representsthe current flowing through the switch elements. These output lines areconnected to the drive element assigned to the particular switchelement. The measurement line 84 leads from the switch element 30 to thedrive element 66, the measurement line 88 leads from the switch element32 to the drive element 74, the measurement line 92 leads from theswitch element 34 to the drive element 70 and the measurement line 96leads from the switch element 36 to the drive element 78.

In the preferred example shown in FIG. 1, additional input lines areconnected to the drive elements for actuating the respective assignedswitch elements. The drive element 66 is connected via the line 98 tothe input E1 of the arrangement 12. In addition, a line 110 is connectedfrom the input E1 of the arrangement 12 (that is, from the line 98) todrive element 70 via an inverter (not shown). A line 112 leads frominput E2 to drive element 74; whereas, a line 114 leads from the sameinput (that is, from the line 112) to drive element 78 via an inverter(not shown).

In another advantageous embodiment and as shown in FIG. 3, the switchelements 30 and 36 can be connected to E1 and the switch elements 32 and34 can be connected to E2 in a conventional manner.

In addition, the drive element 66 is connected via a line 100 to theinput D1 of arrangement 12. In a like manner, the input D1 is connected,as required from the line 100, to the other drive elements 70, 74 and 78which is shown in FIG. 1 with the same reference numerals.

In a preferred embodiment, a second microcomputer 11 is present which isconnected via the input D2 of arrangement 12 in the same manner to theelements of the arrangement 12 as the input D1 (see line 101). Forreasons of reliability, the microcomputer affords the possibility toswitch the output stage off and to again switch the output stage on. Thecomputer 11 then does not control the output stage. The computer 11 can,for example, be a computer for controlling gasoline injection and/orignition. The input signals on the inputs D1 and D2 are logicallyOR-coupled in the arrangement 12.

A further component of the arrangement 12 defines the monitoring unit80. This monitoring unit is multiply connected to the drive elementswhich is only sketched in FIG. 1 for reasons of clarity.

A line 102 (FF) connects the monitoring unit 80 to the drive elements.In addition, a line 103 connects the line 102 to the output FF of thearrangement 12. The connecting line 104 (FF2), shown in phantom outline,connects, in an advantageous embodiment, the monitoring unit 80 to alldrive elements.

Furthermore, the lines 118 (I1), 119 (I2), 1010 (I3), 1012 (I4) connectthe monitoring unit 80 to the drive elements 66, 70, 74, 78.

The line 106 is also connected to the monitoring unit 80. This lineconnects the unit 80 to a unit 1014 which can also be a component of theunit 80 and carries out further fault monitorings. A measure for theoperating voltage is supplied via the line 107 to the unit 1014. Ameasure for the temperature of the arrangement 12 (of the chip, of thesubstrate) is supplied via a line 108. A measure for the referencevoltage is supplied via line 109 and a measure for the voltage of thecharging pump of the switch elements 30 and 32 is supplied via the line111. These values are compared to upper and/or lower limits in thecomparator elements 1016, 1018, 1020, 1022 and the respective outputsignals are OR-coupled (gate 1024). The output line of the gate 1024 isthe line 106.

Lines 120 and 122 connect the monitoring unit 80 to the inputs E1 andE2. Furthermore, the unit 80 is connected to the inputs D1 and D2 (lines100, 101).

The principal way in which the arrangement in FIG. 1 operates is shownbelow with respect to the preferred application of an electronic motorpower control for controlling a throttle flap of an internal combustionengine. The motor 62 or the step motor equipped with the winding 62 isconnected to the throttle flap. Operating variables such as acceleratorpedal position, engine rpm, engine temperature, et cetera, are suppliedfrom the measuring devices 18 to 20 are supplied to the microcomputer 10via the input lines 14 to 16. The microcomputer 10 determines on thebasis of these operating values a drive signal for the arrangement andthis signal is supplied via the lines 22 and 24 in the form of apulsewidth-modulated pulse signal. A desired value for the drive signalcan also be supplied from the microcomputer 11. This drive signal isadjusted by the computer 10 in the context of a position control.

The drive signals are then inverse with respect to each other. Statedotherwise, with the control signal applied to E1, either the switchelement 30 is switched on or the switch element 34 is switched off as aconsequence of the inverter or vice versa. In a similar manner, theswitch element 32 is switched off at the same time by the signal appliedto the input E2 and the switch element 36 is switched on by theinverter. This permits a rapid current buildup and current reduction andtherefore a precise positioning of the motor.

For normal operation, the following operating states of the arrangement12 are given:

    ______________________________________                                                  Switch Elements                                                     D     E1      E2    30    32  34    36  Effect                                ______________________________________                                        0     X       X     A     A   A     A   OFF                                   1     0       0     A     A   E     E   free running                          1     0       1     A     E   E     A   neg. current                          1     1       0     E     A   A     E   pos. current                          1     1       1     E     E   A     A   free running                          ______________________________________                                    

The procedure of the invention to protect and to monitor the arrangement12 will be shown below with respect to FIG. 2. FIG. 2 shows a detailedillustration of the monitoring unit 80 as well as the drive element 66.The same elements of FIG. 1 which are in FIG. 2 are identified by thesame reference numerals and will not be explained below in greaterdetail.

Furthermore, it is noted that the configuration of the drive element 66corresponds to the configurations of the drive elements 70, 74, and 78which are not shown in FIG. 2 for reasons of clarity. The illustrationof the input E2 is likewise not shown in FIG. 2 for reasons of claritybecause this input is of no importance in connection with theillustration at switch element 30. For this reason and with respect toswitch elements 32 and 34, the input E2 must be connectedcorrespondingly in lieu of input E1.

In the preferred embodiment shown in FIG. 2, the switch element 30comprises an MOS field-effect-transistor 200 having a gate terminalwhich is connected to the line 64 and having source and drain terminalsconnected to lines 38 and 44, respectively. In measuring element 82, thecurrent I_(T) is detected by the transistor, for example by a componenthaving a resistance and is conducted via the line 84 to the driveelement 66. Alternatively, and in an advantageous manner, a so-calledcurrent-sensing MOSFET can be utilized as the transistor and thistransistor includes a current measuring output.

The drive element 66 is essentially made up of three elements: a logiccircuit 202, a drive circuit 204 having current limiting and, ifrequired, a charging pump and a comparator 206. The logic circuit 202 isconfigured essentially as an AND-gate. The following are connected tothe logic circuit 202: the lines 98 from the input E1, the line 100 fromthe inputs D1 and D2 which are joined in the OR-gate 201, the lines 102and 104 from the monitoring unit 80 and the output line 208 of thecomparator 206. The logic circuit 202 is connected via line 210 to thedrive circuit 204. The line 84 is connected to the drive circuit 204 inthe same manner as to the comparator 206. The output line of the drivecircuit 204 defines the line 64 which connects the drive element 66 tothe switch element 30. The output line of the comparator 206 leads, onthe one hand, via the line 208 to the logic circuit 202 and, on theother hand, to the monitoring unit 80 via the line 118.

The monitoring unit comprises essentially the following components:incrementing/decrementing means (fault counter) 212 and the logiccircuit 214 which is essentially configured as an OR-gate.

The line 120 from input E1 (that is, from the line 98), the line 116from input D1/D2 (that is, from the line 100) as well as the line 222from the logic circuit 214 are all connected to the counting means 212.The output line of the counting means 212 (that is, the monitoring unit80) defines the line 102 which is connected to the drive element 66(that is, the logic circuit 202). The line 103 leads from line 102 tothe output FF of the arrangement 12.

The line 118 from drive element 66 as well as corresponding lines 119,1010 and 1012 from drive elements 70, 74 and 78, respectively, are allconnected to the logic circuit 214.

The line 106 leads as line 104 from the monitoring unit 80 to the driveelement 66.

As mentioned above, the preferred embodiment of FIG. 2 is shown only inconnection with the switch element 30 and the drive element 66. In acomplete illustration, the lines 100, 102 and 104 would not only beconnected to drive element 66 but also to the other drive elements 70,74 and 78. Furthermore, and in a preferred embodiment, the line 122 frominput E2 (that is the line 112/114) is connected to the monitoring unit80 in addition to the line 120 from input E1 (that is, the line 98).These lines are connected to counting means 212, for example, via anOR-connection with the line 120 in order to obtain an even evaluation ofthe fault states from positive and negative current flowing in theconsumer 62.

In the following, the operation of the arrangement of FIG. 2 will bedescribed for a fault-free operation.

The microcomputer 10 generates pulse drive signals which are inverse toeach other and which are formed by inversion from a signal in oneembodiment and are outputted on the lines 22 and 24 to the inputs E1 andE2 of the component 12. In the fault-free operation, the signals, whichare applied to the logic circuit 202, are of such a form that thepulsewidth modulated input signal, which is supplied via the line 98 tothe drive element 66, is transmitted further to the line 210. In thedrive circuit 204, the pulsewidth modulated drive signal, which issupplied via the line 210, is processed for driving the transistor. Forexample, the circuit 204 includes a voltage overshoot circuit (chargingpump) which ensures the switching on or switching off of the transistor.The transistor is then switched on and switched off in a clocked mannerin correspondence to the pulsewidth modulated drive signal. The switchelement 34 is switched off and switched on inversely and synchronouslywith respect thereto. The switch elements 32 and 36 are actuated asshown above by the input signal at the input E2 so that an averagecurrent flows through the consumer 62 which corresponds to thepulsewidth of the pulsewidth modulated signal. The positioning iseffected with this current.

During operation, various types of faults can occur. Especiallydangerous are short circuits or short circuit like fault conditionswhich can occur, for example, as a short circuit in the consumer 62 oras a short circuit in the supply lines to the consumer 62 to ground orto the operating voltage. Furthermore, an undefined behavior of theconsumer can occur when there is a drop below a pregiven minimumthreshold by the operating voltage or by exceeding a maximum thresholdof the operating and reference voltages. Furthermore, unwanted operatingconditions can occur when there is a thermal load on the component 12.

According to the invention, protective mechanisms are provided incomponent 12 for the above-mentioned types of faults.

The starting point of short circuit protection is the detection of thecurrent through the switch elements. A current measuring element isassigned to each switch element. In the example of FIG. 2, this is themeasuring element 82. The detected current is, on the one hand,connected to the drive element 204 which has a current limiting circuit(for example, realized by diodes) which influences the drive signal inthe sense of current limiting to a pregiven maximum value I_(Tmax). Thismeasure rapidly limits the current in the range of 2 to 5 microseconds.Furthermore, the current measured value is supplied to the comparator206 which compares the current to a pregiven maximum value. If thecurrent exceeds this maximum value or if this current is the same as themaximum value (current limiting), then the comparator 206 changes thesignal level at its output. In this way, the logic circuit 202 preventsthat the drive signal, which is supplied via the line 98, reaches theline 210.

Thereafter, the fault counter is increased by 1 by the comparator 206via the line 118 and the logic circuit 214. This slower circuitcomponent then leads to a switchoff of the transistor via the logiccircuit 202.

In a preferred embodiment, the maximum values of the current limitingcircuit and of the comparator are different in amount with the maximumvalue of the comparator being less than that of the current limiting.

By switching off the transistor, the current flowing therethrough dropsso that the comparator output signal again changes its level. In thisway, it is made possible that, with the next pulse of the drive signal,a new switch-on attempt of the transistor is carried out. The drivesignal is conducted via the line 98 to the logic circuit 202. If a shortcircuit is still present, then, according to the above embodiment, thetransistor is again switched off and the counter 212 is incrementedby 1. If the fault counter reaches a specific value such as 10, then itchanges the level on its output line 102 so that, on the one hand, thetransistor is permanently switched off via the logic circuit 202, thatis, a pulse of the input signal does not lead to another attempt toswitch on the switching element and, on the other hand, a faultannouncement is transmitted to the microcomputer via the output line 103and 28. What is significant is that, in this case, not only is theswitch element 30 switched off but all switch elements are switched off;whereas, the output signal of the comparator 206 effects only theswitch-off of the switch element assigned to this comparator.

In summary, after Imax is exceeded by the current in the transistor, acurrent limiting is first activated and then the fault counter is setvia coupling of the drive signal E1 or E2 with the current comparator.

If the detection is made when switching off the transistor that thefault is no longer present, then the fault counter 212 (if its counterposition is greater than 0) is decremented by 1 via the pulse of thedrive signal. In this way, an unwanted addition of individual shortcircuits over a long time interval is prevented which could lead to aswitch-off of the component 12.

In another advantageous embodiment, the fault counter is decrementedduring the next repeat switch-on attempt of the transistor when a faultis no longer present and the counter position is greater than 0.

The comparator output lines 119, 1010 and 1012 of the other switchelements of the full bridge output stage are connected to the logiccircuit 214. The logic circuit 214 essentially defines a logicOR-function. Accordingly, each individual fault on one of thetransistors leads to influencing the fault counter 212. This means that,in the fault counter, the fault conditions of the switch elements areadded; that is, each of the four switch elements can increment the faultcounter in the case of a short circuit. This improves the operationalreliability considerably because critical fault conditions such as inthe area of the consumer lead very rapidly to reactions without it beingnecessary to limit the availability for individual faults.

The output stage can only be switched on again via the input D1 or D2which decrements the fault counter via a corresponding flank change bythe microcomputer 10 or 11 and the logic circuit 202 is again activated.This can, for example, take place in that the microcomputer evaluatesthe fault data supplied via the output FF and decides pursuant topregiven criteria, whether the component 12 should again be switched onor not.

This procedure affords the advantage that short disturbances as causedby disturbing radiation do not lead to switching off the entire outputstage.

In the preferred embodiment of an electronic throttle flap control, theoutput stage is driven at a frequency of approximately 15 to 25 kHz sothat the switch-on and switch-off times of the pulsewidth modulatedsignal can be very short. The presented type of short circuit protectionis suitable for this environment. Furthermore, the described method alsomakes possible the detection of short circuits which occur only in thecase of a drive such as, for example, a short circuit of the consumer 62to ground.

Further protective measures can be provided.

The unit 1014 is supplied with a temperature signal via the line 108.This temperature signal represents the temperature of the component 12.This thermal protection covers the case of a fault wherein thepulsewidth modulated signal drives the switch element 30 within a timeless than 2 to 5 microseconds so that the above-described protectivemechanism cannot respond. Accordingly, in the switch loop 1022, thetemperature signal which is supplied via the line 108, is compared to athreshold value so that a corresponding change of signal follows for anovertemperature. This signal change is conducted via the gate 1024, theline 106 and the line 104 to block the logic circuit 202 and to switchoff the switch element 30 as well as the other four switch elements.

An operation of the arrangement for operating voltages outside of apregiven range can be prevented by conducting the operating voltage vialine 107 to the switch loop 1016 which compares the operating voltage tominimum or maximum thresholds. If there is a drop below one thesethresholds or one of these thresholds is exceeded, then the output stageis blocked via the gate 1024, the line 106 and the line 104, that is,the drive of the switch element 30 is blocked as well as of the otherthree switch elements.

In an advantageous embodiment, at overtemperature or overvoltage orundervoltage, the fault counter can be set to a pregiven value which,supplied to the microcomputer, can form a basis for again switching onthe output stage so that the microcomputer can again switch on theoutput stage after a pregiven time, for example, when there is anovertemperature.

These three protective mechanisms can be individually combined or can becombined together with the described short circuit protection.Furthermore, and in a similar manner, the voltage on the charge pump aswell as the logic reference voltage can be evaluated.

An integrated component for a full bridge output stage is advantageousfor driving an electric motor which component includes at least twoinputs E1 and E2 as well as those inputs for connecting the input D1 orD2 and the output FF to the microcomputer and which contains theprotection functions shown.

In a preferred embodiment, measures are provided which lead to theswitch-off of the current supply of the output stage via themicrocomputer in the case of a fault when fault data is transmitted onthe line 28.

In FIG. 3, and in the context of a second preferred realization, afurther embodiment of the procedure of the invention is shown. Theabove-described second drive principle is applied for the four switchelements. The switch elements 30 and 36 are activated by the drivesignal at input E1 and the switch elements 32 and 34 are actuated viathe drive signal of input E2. The pulse-shaped drive signals at theinput E1 and E2 can be inverse relative to each other. The inversion ofthe input signal at the input E1 can be carried out preferably in themicrocomputer 10 as well as via corresponding devices in the arrangement12. The inversion described above of, for example, the signal from theinput E1 to drive the switch element 34 is unnecessary.

The elements, described in FIG. 3 with the same reference numerals as inFIGS. 1 and 2, have the same function as explained above and aretherefore not described in greater detail. Furthermore, in FIG. 3,switch element and drive element are considered together in one elementfor reasons of clarity.

The input line 300 from input E1 of the arrangement 12 (not shown) leadsto the following: the drive and switch element (30, 66), the drive andswitch element (36, 78) and the monitoring unit 80. Likewise, the inputline 302 leads from input E2 to the following: drive and switch element(32, 74), drive and switch element (34, 70) and monitoring unit 80. Asin FIG. 2, a fault line 102 is connected to each drive and switchelement. Furthermore, a line is connected from each drive and switchelement to the monitoring unit 80 which displays when the pregivenmaximum current is exceeded. These lines 118, 119, 1010 and 1012 areshown in FIG. 1.

Furthermore, the monitoring unit 80 has the following: the input lines100 and 101 from the inputs D1 and D2, an input line 107 on which asignal is supplied representing an increase above or a drop belowpregiven limit values by the battery voltage, a line 108 which suppliesa signal which indicates an increase above a pregiven chip temperature,a line 111 which conducts a signal displaying a drop of the voltage onthe charge pump of the switch elements 30 and 32 and a line 109 on whicha signal is supplied which indicates a drop below a pregiven limit valueby the reference voltage supplying the logic components of the outputstage.

The principle of the embodiment of the monitoring shown in FIG. 3 isbased upon the situation that both half bridges (switch elements 30 and36/switch elements 32 and 34) are monitored separately from each other.For this purpose, the line 118 and 1012 are connected in the monitoringunit 80 to an OR-gate 304 having output line 306, on the one hand, totime element 308 and, on the other hand, to incrementing input 310 of acounter means 312. The line 300 is connected from input E1 to thedecrementing input 314 of counting means 312. The output line 316 oftime element 308 as well as the output line 318 of counting means 312are connected to a further OR-gate 320. The output line 322 of theOR-gate 320 is connected to a third OR-gate 324. The output line 326 ofOR-gate 324 is connected to the clock input 328 of the D-flipflop 330.Correspondingly, the line 1010 as well as 119 is connected to an OR-gate332 with respect to the second half bridge (switch elements 32 and 34).The output line of OR-gate 332 is connected to a time element 336 aswell as to the incrementing input 338 of counting means 340. The line302 is connected from input E2 to the decrementing input 342 of countingmeans 340. The output line 344 of time element 336 as well as the outputline 346 of counting means 340 is connected to an OR-gate 348. Theoutput line 350 of OR-gate 348 is, in turn, connected to the OR-gate324. A line 352 is connected to the D-input of flipflop 330. The line352 is clamped to a logic 1. The output line 354 is connected to theoutput Q of the flipflop 330 and leads to a NOR-gate 356. The secondinput line 358 of NOR-gate 356 comes from a further OR-gate 360. Theinput lines 100, 101, 107, 108, 109, 111 are logically connected to eachother in the OR-gate 360. The line 358 leads to the reset inputs of theflipflop 330 as well as of the counting means 340 and 312. The outputline of the NOR-gate 356 defines the output line 102 of the monitoringunit 80 which, on the one hand, leads to the drive and switch elementswhile on the other hand, leads to the output FF of the arrangement 12.

The operation of the arrangement of FIG. 3 is described below. Eachswitch element is preferably configured as a current-sensing FET andtransmits an increase above an internally pregiven maximum current viathe corresponding output of its drive element. In this way, each switchelement is monitored as to overcurrent. If the current through a switchelement exceeds the inputted maximum value, then a corresponding signalis transmitted via the lines 118, 1012, 1010 or 119 to the monitoringunit 80. There, the signal is transmitted via the corresponding OR-gate304, 332, on the one hand, to start the time element 308 or 336 and, onthe other hand, to increment the counter 312 or 340. The current throughthe switch element is then limited to a maximum value in the driveelement as shown in FIG. 2. What is essential is that each half bridgehas only one time element and one counting means assigned thereto sothat overcurrents in the switch elements of a half bridge can be appliedindividually as well as in combination for fault monitoring. The timeelement 308 or 336 generates an output signal when the overcurrentsignal of one of the switch elements of a half bridge or both switchelements exceeds, in its time-dependent sum, a predetermined value suchas 50 microseconds. This output signal is conducted to the clock input328 of the fault flipflop 330 on the one hand via the line 316, theOR-gate 320, the line 322, the OR-gate 324 and the line 326 and, on theother hand, via the line 344, the OR-gate 348, the line 350, the OR-gate324 and the line 326. A level change at the output Q is generated in thefault flipflop 330 by the level change at the input 328. This levelchange leads via the line 354 and the NOR-gate 356 to a level change onthe output line 102 and therefore to setting the fault flag FF. Thesetting of the fault flag FF leads to the switch-off of all switchelements via the line 102 and leads to the fault announcement via theline 28 to the microcomputer 10. The two half bridges are then evaluatedalternatively with respect to each other so that a fault can be detectedwhen either one switch element of a half bridge, both switch elements ofa half bridge or one switch element in both half bridges is defective.An overcurrent fault condition can however only be detected inaccordance with this procedure when the period duration of the clockeddrive signal is greater than the time duration pregiven in the timeelements 308 or 336. This is so because after the termination of theactive phase of the clocked drive signal, the corresponding switchelements are switched off and therefore the overcurrent detectionbecomes unavailable. In order to establish control over this operatingcondition, counting means 312 and 340 are provided which are incrementedwith each detected overcurrent and which are decremented with each drivepulse or a pregiven plurality of drive pulses when no fault is present.For this purpose, the drive frequency can be halved in an advantageousmanner so that the fault counter is decremented only with each secondperiod. If the contents of the fault counter exceed the correspondinglimit value, then the counting means emit signals via their output lineswhich lead to the setting of the fault flag FF in the above-describedmanner.

The fault detection is carried out independently of the drive signal viathe time elements. Even when a switch-on signal for the switch elementscontinuously appears on the inputs E1 or E2 and a short circuit occursduring this condition, then the output stage is switched off after thepregiven time has elapsed and the fault flag is set. The integratedoutput stage is configured in such a manner that, during the pregiventime of preferably 50 microseconds, the output stage tolerates thecurrent limited to the maximum current. Further functions in addition tothe described monitoring measures are provided according to FIG. 3.First, the output stage can be switched off via the inputs D1 and D2 andthe fault flag FF can be set via the line 358. Secondly, a flank changeon the lines 100 or 101 can lead to resetting of the counters and theflipflop 330 and activate the output stage.

In addition, further monitoring measures are provided which monitor thefollowing as to specific limit values: the operating voltage, the logicreference voltage, the charge pump voltage and the chip temperature.This takes place in separate comparator devices which are not shown inFIG. 3 for reasons of clarity. the operating voltage UBat is monitoredas to a lower limit value and, if required, to an upper limit value. Ifthe operating voltage drops below this limit value, then the fault flagFF is set by means of a corresponding signal on the line 107 via theline 358 and the reset input of the flipflop 330. Likewise, the logicreference voltage US is monitored as to a lower limit value. If thereference voltage drops below this limit value, then a correspondingsignal on the line 109 switches off the output stage. The monitoring ofthe charge pump voltage as to a lower limit value leads to the sameresult and has great significance, as does the monitoring of theoperating voltage, especially in the switch-on operation. During theswitch-on operation, the operating voltage drops below the limit valuewhereas the charge pump voltage increases from zero only after switch-onso that this voltage too is below a limit value. In this way, thecorresponding signals are generated on the lines 107 and 109 which leadsto a resetting of the counters 312, 340 and the flipflop 330. In thisway, a defined output state of the output stage is obtained. A furthermonitoring relates to the chip temperature. If this chip temperatureexceeds a specific value, then the output stage is switched off in amanner described above.

In addition to the embodiments described above, the individualmonitoring measures described can be utilized in any desiredcombination. Thus, an output stage can be provided wherein only the timeelement monitoring is provided or only the fault counter monitoring isprovided. Furthermore, output stages can be provided which undertakemonitoring of half bridges or monitoring of individual switch elements.Furthermore, it is not necessary to activate the output stage viaexternal inputs or, with respect to monitoring operating variables ofthe output stage, the suitable variables can be selected. Also, eachswitch element can be assigned a time element and/or a fault counter.

We claim:
 1. An arrangement for operating a consumer in a vehicle, thearrangement comprising:at least two switch elements operativelyconnected to said consumer through which a current can flow;microcomputer means for generating at least one drive signal to actuatesaid switch elements to influence said current through said consumer; amonitoring device for monitoring the operability of said arrangement andsaid monitoring device including: detecting means for detecting therespective currents through said switch elements; means for providing apregiven value for said currents; and, monitoring means for monitoringthe respective currents through said switch elements to determine whensaid currents reach or exceed said pregiven value; limiting means forlimiting the current through at least one of said switch elements to amaximum value when said current through said one switch element exceedssaid pregiven value; and, circuit means for switching off said switchelement when said current through said one switch element has exceededsaid pregiven value for a pregiven time duration.
 2. The arrangement ofclaim 1, wherein said drive signal is a pulsewidth modulated signalwhich is supplied to the particular switch element via drive elements.3. The arrangement of claim 1, further comprising: a full bridge outputstage with each half bridge being assigned a time element and/orcounting means and faults are detected when the maximum current isexceeded in one or both switch elements.
 4. The arrangement of claim 1,wherein said two switch elements define an output stage connected tosaid consumer; and, said circuit means being adapted to switch off saidoutput stage when said pregiven value through at least one of saidswitch elements is exceeded for said pregiven time duration.
 5. Anarrangement for operating a consumer in a vehicle, the arrangementcomprising:at least two switch elements operatively connected to saidconsumer through which a current can flow; microcomputer means forgenerating at least one drive signal to actuate said switch elements toinfluence said current through said consumer; a monitoring device formonitoring the operability of said arrangement and said monitoringdevice including: detecting means for detecting the respective currentsthrough said switch elements; means for providing a pregiven value forsaid currents; and, monitoring means for monitoring the respectivecurrents through said switch elements to determine when said currentsreach or exceed said pregiven value; limiting means for limiting thecurrent through at least one of said switch elements to a maximum valuewhen said current through said one switch element reaches or exceedssaid pregiven value; circuit means for switching off said switch elementwhen said current through said one switch element has reached orexceeded said pregiven value for a pregiven time duration; said drivesignal being a pulsewidth modulated signal which is supplied to theparticular switch element via drive elements; said drive elements beingso configured that, when the current flowing through the particularswitch element exceeds said pregiven value, an internal current limitingis undertaken by influencing said drive signal.
 6. The arrangement ofclaim 5, wherein said arrangement further comprises counting means whichis incremented by 1 and/or a time element which is started when saidmaximum value is exceeded by the current through said one switchelement.
 7. The arrangement of claim 6, wherein the particular switchelement is again switched on with the next drive pulse of the drivesignal when a fault state of the switch element is detected.
 8. Thearrangement of claim 7, wherein the arrangement further comprisescounting means which is decremented by 1 by the drive pulses when afault state is not present.
 9. The arrangement claim 8, wherein a faultsignal is generated when said counting means position exceeds apredetermined value and/or when a pregiven time has elapsed, which leadsto a complete switch-off of said arrangement.
 10. The arrangement ofclaim 9, wherein protection against overtemperature, undervoltage orovervoltage of the operating voltage and/or the logic reference voltageis provided and protection against undervoltage of a charging pumpdriving the switch elements is provided.
 11. The arrangement of claim10, wherein switching said arrangement on again is provided by themicrocomputer.
 12. An arrangement for operating a consumer in a vehicle,the arrangement comprising:at least two switch elements operativelyconnected to said consumer through which a current can flow;microcomputer means for generating at least one drive signal to actuatesaid switch elements to influence said current through said consumer; amonitoring device for monitoring the operability of said arrangement andsaid monitoring device including: detecting means for detecting therespective currents through said switch elements; means for providing apregiven value for said currents; and, monitoring means for monitoringthe respective currents through said switch elements to determine whensaid currents reach or exceed said pregiven value; limiting means forlimiting the current through at least one of said switch elements to amaximum value when said current through said one switch element reachesor exceeds said pregiven value; and, circuit means for switching offsaid switch element when said current through said one switch elementhas reached or exceeded said pregiven value for a pregiven time durationand a fault is detected when said maximum current is exceeded and saidfault is stored in a fault memory which can be reset and which can bereset by said microcomputer means.
 13. An arrangement for operating anelectric motor in a vehicle, the arrangement comprising:a full bridgeoutput stage for driving an electric motor; said output stage includingswitch elements; a microcomputer for supplying a pulsewidth modulatedpulse-shaped drive signal to said output stage; means for detecting therespective currents in said switch elements and for monitoring saidcurrents to determine when said currents exceed a pregiven value; saidarrangement defining an integrated component including: a drive input;an enable/disable input; terminals for said electric motor and an outputfor fault data; and, means for coupling to said microcomputer; means forlimiting the current through one of said switch elements when thecurrent through said one switch element has exceeded said pregivenvalue; and, switch-off means for switching off said one switch elementof said output stage when the current through said one switch elementhas exceeded the maximum current therein for a pregiven time duration.14. The arrangement of claim 13, wherein said electric motor actuates apower control element of an internal combustion engine.
 15. Thearrangement of claim 14, wherein said power control element is athrottle flap.
 16. The arrangement of claim 14, wherein said powercontrol element is an injection pump.